The present invention relates to novel ruthenium complex compounds, especially diammonium ruthenium diethylenetriaminepentaacetate or a hydrate thereof, which are water-soluble and stable both in the atmospheric condition and an aqueous solution, and a process for producing the both.
Ruthenium metal is a hard, brittle, silver-white and noble metal belonging to the platinum group. Currently, this metal is mainly obtained as a by-product when platinum is extracted from anode slime precipitated in an electrobath in a process for electrorefining nickel or copper. The ruthenium metal has been used for a corrosion-resistant protective metal layer, since it is insoluble in any acid in the absence of oxygen and excellent in corrosion resistance.
Ruthenium (IV) oxide [RuO2], which is the most stable of ruthenium oxides, has the similar properties against acids to the ruthenium metal. Ruthenium is also known as an element having the effect of hardening platinum, palladium and the like. For instance, Pd-4.5% Ru alloy has been known as a noble metal for an ornament, Pt-10% Ru alloy as an ornamental metal or an electric contact material, and Osxe2x80x94Ru alloy as a material for a pen point of a fountain pen.
In addition, most of platinum group elements exhibit excellent catalytic activities for hydrogenation, oxidation, dehydrogenation and carbonylation. It has been known that ruthenium metal or complexes thereof also exhibit excellent catalytic activities for various reactions. For example, ruthenium metal has been proved to be sufficiently active as a catalyst for hydrogenation of inorganics such as ammonia synthesis and carbon monoxide, and hydrogenation of organics such as carbonyl compounds and aromatic compounds. Some ruthenium complexes also have been known as sufficiently active or selective catalysts for hydrogenation of an unsaturated bond, and others as a catalyst for hydrogenation using carbon monoxide.
Moreover, it has been known that ruthenium forms a variety of complexes and the typical examples includes a chloride of [(NH3)5RuIIIxe2x80x94Oxe2x80x94RuIV(NH3)4xe2x80x94Oxe2x80x94RuIII(NH3)5]6+, which is called ruthenium red. The chloride exhibits an intense red color when dissolved in water and, therefore, it is used for an oxidation-reduction indicator, dyeing of living tissue, and so on. In addition, since the usage in a semiconductor field is currently considered, it is expected that the demand grows increasingly in the future.
By the way, it has been known that most halides and complex compounds of the conventional ruthenium compounds are water-soluble. However, it is difficult to handle these halides because of the hygroscopic property. Moreover, since the halides are unstable in the aqueous solution, the halides are transformed into black hydrides due to the hydrolysis, or are decomposed into oxyhalides and hydrogen halides. Further, the complex compounds are generally not stable enough for long-term storage in the aqueous solution, although many of them are known to be stable in the air.
The present invention has been accomplished under these circumstances, and an object of the present invention is to provide novel ruthenium complex compounds or a hydrate thereof, which are water-soluble and excellent in handling and, moreover, stable both in the air and in an aqueous solution so as to withstand ling-term storage, and a process for producing the both.
According to an aspect of the present invention, the ruthenium complex compounds, which can achieve the aforementioned object, include diammonium ruthenium diethylenetriaminepentaacetate represented by the following formula (1) or the hydrate thereof. 
According to another aspect of the present invention, the process for producing the diammonium ruthenium diethylenetriaminepentaacetate represented by the above-mentioned formula (1) or the hydrate thereof includes conducting a solid-liquid reaction in an aqueous medium between diethylenetriaminepentaacetic acid and ruthenium salt which is water-soluble to obtain slurry, subjecting the slurry to a solid-liquid separation to remove a solid phase portion therefrom, and dissolving the solid phase portion into aqueous ammonia to obtain a complex compound. Alternatively, from the solution obtained by dissolving the solid phase portion into the aqueous ammonia, a hydrate of diammonium ruthenium diethylenetriaminepentaacetate may be crystallized so as to obtain the crystals of the hydrate thereof.
Further, the crystallized hydrate may be dried by heating, to obtain an anhydrate of the diammonium ruthenium diethylenetriaminepentaacetate.